1. Field of the Invention
The present invention relates to a discharge control technique that performs landing with several kinds of dot sizes by changing the droplet quantity that particularly forms one dot in association with a device and a method for driving a liquid discharge head, a liquid discharge apparatus, and an ink-jet apparatus.
2. Description of the Related Art
In an ink-jet apparatus, a so-called multi-drop type gradation printing is known which changes the number of ink jet drops being jetted to 1, 2, 3, . . . with respect to printing data that corresponds to a record of one dot (landing point of one pixel) when recording an image by forming dots with ink drops on a recording medium such as paper or the like, and forms one-dot droplets by joining the plurality of ink drops (JP1999-348320A (JP-H 11-348320A) and JP-2006-224471A). By adopting this method, a high quality image can be formed.
In the multi-drop type gradation printing, there is a method in which the speed of an ink drop that is discharged later is sequentially set to be higher than the initial ink drop discharge, the ink drop that is discharged later reaches the preceding ink drop to join the preceding ink drop during their flight, and thus one droplet is landed on the recording medium (JP-2006-224471A). This method is realized by consecutively applying a driving pulse voltage to a piezoelectric actuator so that the amplitude of pressure waves in an ink chamber gradually increases during ink discharging.
JP1999-348320A (JP-H 11-348320A) discloses that a reference driving signal is made in which jet pulses the number of which is the maximum number of jets are arranged at predetermined time intervals, and a driving signal to be applied is made by removing a predetermined number of jet pulses sequentially from the front of the reference driving signal to acquire the dot gradation.
Further, JP-2006-224471A describes a technique to make the droplet speed between discharged ink drops constant through making different drop quantities in order to form dots having different sizes (large dot, medium dot, and small dot).